Function accessor

docs/app/js/sanddance-app.js:106501–106505

(fn, fields, name)

parcelHelpers.export(exports, "zoomPow", ()=>zoomPow);
parcelHelpers.export(exports, "zoomSymlog", ()=>zoomSymlog);
function accessor(fn, fields, name) {
    fn.fields = fields || [];
    fn.fname = name;
    return fn;
}
function accessorName(fn) {
    return fn == null ? null : fn.fname;
}